1. Field of the Invention
The present invention relates generally to a method for reading battery status of a battery of a portable computer, and in particular to a method for reading battery status of the portable computer in order to save system resources of a central processing unit of the portable computer.
2. Description of the Prior Art
Windows-based operation systems, such as Windows XP, Windows 2000, both being available from Microsoft Corporation, are currently used in computers. The Windows-based operation systems include the Advanced Configuration and Power Interface (ACPI) for power management. The ACPI controls the power management for hardware of the computer system, including notebook computers, desktop computers and server computers.
The ACPI is a standard power management system interface developed by the computer industry, serving as a common power management interface between the computer operation system (software) and the computer (hardware). The standard power management interface allows the computer manufacturers and designers to share the same power management technique for software portability. The ACPI allows the operation system to manage the power consumption of peripheral devices of a computer system based on a predetermined algorithm. For example, the ACPI commands a hard disk drive to enter “power saving mode” or simply shutting down the hard disk drive if it is not operated for a predetermined period of time. The hard disk drive is only allowed to resume operation if it is desired by a computer user.
A primary advantage of a portable computer, such as a notebook computer, is the portability, which allows a user to carry the computer with him or her. Due to the portability, the portable computer is powered by internal power sources, such as a battery. Since the battery has a limited power capacity, power management of the battery becomes an important issue of vital importance for the portable computer.
Typically, the portable computer comprises a central processing unit operating with a System Basic Input Output System (commonly referred to as BIOS) and a keyboard controller. The keyboard controller comprises an embedded micro-controller, a Keyboard Basic Input Output System (commonly referred to as Keyboard BIOS), memory and other interfaces. As mentioned previously, the portable computer is powered by a built-in power source, such as a battery. To monitor the status of the battery, the keyboard controller comprises a battery status monitoring interface. The ACPI-based operation system of the portable computer accesses the battery status information of the keyboard controller via ACPI machine language (AML).
The operation system or system BIOS of the portable computer is designed to read the battery status 2–3 times consecutively. However, due to the fact that the keyboard controller is a device that operates slower than the central processing unit of the computer system, when the central processing unit is scheduled to read the battery status at the same moment that it is busy with a particular task, such as playing Digital Video Device (DVD), a temporary pause of the DVD image may be observed. In other words, periodically reading battery status may slow down the performance of the computer.